In wireless data communication networks, it is foreseeable that mobile station users will travel from one base station zone to another base station zone while using the same application supported by a remote server on a computer network, such as the Internet. Thus, the base stations change, but the remote server supporting the application remains the same.
A personal computer user accessing a remote electronic mail (email) account on a moving train provides a good example of a wireless data communication application. It is desirable for the user that the session be uninterrupted, meaning that neither disconnection nor retraining occur while reading and/or responding to received email. Disconnection means that a loss of communication with the remote server has occurred. Retraining means that the wireless modems supporting the wireless communication has to be retrained. Retraining may also require instantiating a new point-to-point protocol (PPP) session over a new network path from the remote server through the next base station.
In network environments having a circuit switched infrastructure composing much of today's networks, a base station controller (BSC) switches a circuit in a base transceiver station (BTS) to maintain a persistent state during the duration of a call. When the mobile station moves to a next BTS zone, as described above, the BSC switches circuits in the corresponding BTS, for, again, the duration of the call or until the mobile station enters yet another BTS zone.
FIG. 1 is a schematic diagram of a network 100 using prior art circuit switching technology. A mobile station 105 includes a personal computer (PC) 110 coupled to a modem 120. The modem 120 provides for wireless communications to base stations, BTS 1 130a and BTS2 130b. Each of the base stations is coupled to a base station controller (BSC) 140. The base station controller 140 is further coupled to a gateway 150. The gateway 150 provides network communications to a wide area network, such as the Internet.
The mobile station 105 initially establishes a wireless link 123 to BTS1. The wireless link 123 is part of a first link 143 that spans from the mobile station 105 to the gateway 150.
The base station controller 140 supports the first link 143 by allocating channels for the entire duration of the call between the mobile station 105 and the gateway 150 while the mobile station 105 communicates with a remote server (not shown). A first circuit identifier (“cid”) 132 identifies the circuits that remain in the persistent state for the entire duration of the call.
When the mobile station 105 moves to a zone within range of BTS2 130b, the mobile station 105 creates a second wireless connection 126 to BTS2 130b. The second wireless connection 126 is part of a second link 146 that spans between the mobile station 105 and the gateway 150. Here, the base station controller 140 allocates a second set of channels for the entire duration of the call. The second set of allocated channels are identified by a second circuit identifier 64. At a point where one of the network elements—the mobile station 105, base station 130a, base station controller 140, or gateway 150—determines that the first link 143 should be terminated, the base station controller 140 deallocates the circuits identified by the first circuit identifier 132. The circuit identified by the second circuit identifier 64 continues to remain in a persistent state throughout the duration of the call.